WASHINGTON (AP) - The Obama administration struggled behind the scenes to determine how much oil spilled in the Gulf of Mexico from a BP well this year and defended estimates that for months were inaccurate, according to thousands of government e-mails.
A senior scientist who led the federal effort, Bill Lehr of the National Oceanic and Atmospheric Administration, noted that the administration went public with a summary of estimates before experts could finish their work.
An Environmental Protection Agency memo, one of many showing uncertainty, said, "EPA agrees that the ultimate message to the public will likely be that the oil was successfully dispersed with chemical dispersants, but until we know with some degree of certainty ... we are hesitant to assign distinct percentages at this time."
Lehr said the calculations made public represented "our best guess," adding, "Yes, it is a guess."
The government said this week that its final estimate, of 172 million gallons of oil poring into the ocean between April 20 and July 15, was accurate.
The behind-the-scenes e-mails hint at uncertainties in what the government knew during the summer, even as its scientists wrestled over how to measure oil leaking from a runaway well a mile under the ocean.
EPA Administrator Lisa Jackson was "concerned about the level of certainty implied in the pie and cylinder charts." Another e-mail noticed that a pie chart in a draft of the government's report wasn't actually round: "A pie chart pretty much has to round to 100," NOAA spokeswoman Jennifer Austin wrote.
An e-mail from EPA official Bob Perciasepe to other U.S. officials warned: "I think you are making a mistake on the separate estimates of dispersal but I have no additional arguments other than it is not verifiable and we will be trying to explain it for the rest of our time on this. I will take it up with White House."
Lehr's top boss at NOAA, Jane Lubchenco, cautioned a colleague about how to present the government's findings. "I believe we owe it to everyone to provide the best estimates we can where direct measurements are not possible," she wrote. "We also need to be forthright about how certain we are about each number, which we've done."
The e-mails were obtained by The Associated Press under the Freedom of Information Act.
U.S. officials clearly understood the possible economic consequences of their findings. Anticipating a question in August for an upcoming news conference, a NOAA spokeswoman asked scientists, "What impact, if any, will this report have in determining BP's financial liability for this spill?" The answer: The U.S. can fine BP up to $4,300 per barrel of oil that is counted as leaked.
The documents released Wednesday by the Commerce Department,NOAA's parent agency, were significant because they revealed conversations among scientists working on the forecasts of oil in the Gulf. The government released 5,817 pages of files late in the afternoon on the eve of Thanksgiving, traditionally a period when few people are paying attention to news reports because of holiday travel.
Measuring the spill accurately was important to how to respond appropriately and to the administration's credibility. But the government didn't arrive at a reliable estimate until June 15, nearly two months after the disaster began with the explosion and fire aboard the Deepwater Horizon drilling rig.
The government released the files to news organizations and Rep. Ed Markey, D-Mass., who with other lawmakers had asked for the records in August. "The public has a right to know right now what is going on in the Gulf of Mexico, and your report should be analyzed by others right now so that we are sure we got it right," Markey told Lehr, who defended the government's estimates during congressional testimony.
Lehr subsequently told colleagues that none of the terrible places where he studied past oil spills - freezing cold in Alaska, stifling heat in Louisiana or dodging missiles in Arabia - had prepared him for his unpleasant experience in Washington testifying to Congress.
The presidential commission investigating the oil spill concluded last month in an interim report that government mistakes on its estimates led to perceptions that it was incompetent or not candid about the oil spill. It said federal officials underestimated the amount of oil flowing from the well, then also underestimated the amount of oil that had spilled in the Gulf.
The panel also previously criticized statements by President Barack Obama's energy adviser, Carol Browner, who mischaracterized on national TV the government's analysis about where the oil went, saying it showed most of the oil was "gone." In a new study published Tuesday, the government itself acknowledged that its oil calculations were never intended to "provide information about the impact of the oil, nor indicate where the oil is now."
The newly disclosed documents also described leaks and accidental disclosures.
Administration officials worried at times about leaks and inadvertent Internet postings. Dan Leistikow at the Energy Department urgently sought access in June to high-resolution video of the runaway well that had already aired on CNN, which he said was "probably leaked from someone." It turned out that the Coast Guard had the video all along.